An enzyme-linked immunosorbent assay (ELISA) for the determination of mucin levels in bronchoalveolar lavage fluid

Carry-over of host nutrients during sampling enhances undesired growth of Staphylococcus aureus in liquid Amies transport medium

Optimal transportation of bacteria is important for accurate clinical interpretation, quantitative assays, and microbiome studies. A transport medium should ideally keep the bacteria alive without supporting growth or altering the relative proportions of the constituent species. We investigated the effect of nasal mucus and mucin on the growth and survival of two Staphylococcus aureus strains in liquid Amies transport medium at room temperature and 4 °C for 14 days. The study showed that the presence of nasal mucus in microbiological samples stimulated undesired S. aureus growth at room temperature in a dose-dependent manner. These findings underscore that microbiological samples from humans and animals should be stored at 4 °C until analysis to avoid undesired S. aureus growth.

Respiratory Disease following Viral Lung Infection Alters the Murine Gut Microbiota

Alterations in the composition of the gut microbiota have profound effects on human health. Consequently, there is great interest in identifying, characterizing, and understanding factors that initiate these changes. Despite their high prevalence, studies have only recently begun to investigate how viral lung infections have an impact on the gut microbiota. There is also considerable interest in whether the gut microbiota could be manipulated during vaccination to improve efficacy. In this highly controlled study, we aimed to establish the effect of viral lung infection on gut microbiota composition and the gut environment using mouse models of common respiratory pathogens respiratory syncytial virus (RSV) and influenza virus. This was then compared to the effect of live attenuated influenza virus (LAIV) vaccination. Both RSV and influenza virus infection resulted in significantly altered gut microbiota diversity, with an increase in Bacteroidetes and a concomitant decrease in Firmicutes phyla abundance. Although the increase in the Bacteroidetes phylum was consistent across several experiments, differences were observed at the family and operational taxonomic unit level. This suggests a change in gut conditions after viral lung infection that favors Bacteroidetes outgrowth but not individual families. No change in gut microbiota composition was observed after LAIV vaccination, suggesting that the driver of gut microbiota change is specific to live viral infection. Viral lung infections also resulted in an increase in fecal lipocalin-2, suggesting low-grade gut inflammation, and colonic Muc5ac levels. Owing to the important role that mucus plays in the gut environment, this may explain the changes in microbiota composition observed. This study demonstrates that the gut microbiota and the gut environment are altered following viral lung infections and that these changes are not observed during vaccination. Whether increased mucin levels and gut inflammation drive, or are a result of, these changes is still to be determined.

Mucin promotes rapid surface motility in Pseudomonas aeruginosa

An important environmental factor that determines the mode of motility adopted by Pseudomonas aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the viscous gel-like property of the mucus layer that overlays epithelial surfaces is largely due to the glycoprotein mucin. P. aeruginosa is known to swim within 0.3% (wt/vol) agar and swarm on the surface at 0.5% (wt/vol) agar with amino acids as a weak nitrogen source. When physiological concentrations or as little as 0.05% (wt/vol) mucin was added to the swimming agar, in addition to swimming, P. aeruginosa was observed to undergo highly accelerated motility on the surface of the agar. The surface motility colonies in the presence of mucin appeared to be circular, with a bright green center surrounded by a thicker white edge. While intact flagella were required for the surface motility in the presence of mucin, type IV pili and rhamnolipid production were not. Replacement of mucin with other wetting agents indicated that the lubricant properties of mucin might contribute to the surface motility. Based on studies with mutants, the quorum-sensing systems (las and rhl) and the orphan autoinducer receptor QscR played important roles in this form of surface motility. Transcriptional analysis of cells taken from the motility zone revealed the upregulation of genes involved in virulence and resistance. Based on these results, we suggest that mucin may be promoting a new or highly modified form of surface motility, which we propose should be termed “surfing.”

An important factor that dictates the mode of motility adopted by P. aeruginosa is the viscosity of the medium, often provided by adjusting agar concentrations in vitro. However, the gel-like properties of the mucous layers that overlay epithelial surfaces, such as those of the lung, a major site of Pseudomonas infection, are contributed mostly by the production of the glycoprotein mucin. In this study, we added mucin to swimming media and found that it promoted the ability of P. aeruginosa to exhibit rapid surface motility. These motility colonies appeared in a circular form, with a bright green center surrounded by a thicker white edge. Interestingly, bacterial cells at the thick edge appeared piled up and lacked flagella, while cells at the motility center had flagella. Our data from various genetic and phenotypic studies suggest that mucin may be promoting a modified form of swarming or a novel form of surface motility in P. aeruginosa.

Fosfomycin enhances the active transport of tobramycin in Pseudomonas aeruginosa

Elevated levels of mucins present in bronchiectatic airways predispose patients to bacterial infections and reduce the effectiveness of antibiotic therapies by directly inactivating antibiotics. Consequently, new antibiotics that are not inhibited by mucins are needed to treat chronic respiratory infections caused by Pseudomonas aeruginosa and Staphylococcus aureus. In these studies, we demonstrate that fosfomycin synergistically enhances the activity of tobramycin in the presence of mucin. The bactericidal killing of a novel 4:1 (wt/wt) combination of fosfomycin-tobramycin (FTI) is superior (>9 log(10) CFU/ml) relative to its individual components fosfomycin and tobramycin. Additionally, FTI has a mutation frequency resulting in an antibiotic resistance >3 log(10) lower than for fosfomycin and 4 log(10) lower than for tobramycin for P. aeruginosa. Mechanistic studies revealed that chemical adducts are not formed, suggesting that the beneficial effects of the combination are not due to molecular modification of the components. FTI displayed time-kill kinetics similar to tobramycin and killed in a concentration-dependent fashion. The bactericidal effect resulted from inhibition of protein biosynthesis rather than cell wall biosynthesis. Studies using radiolabeled antibiotics demonstrated that tobramycin uptake was energy dependent and that fosfomycin enhanced the uptake of tobramycin in P. aeruginosa in a dose-dependent manner. Lastly, mutants resistant to fosfomycin and tobramycin were auxotrophic for specific carbohydrates and amino acids, suggesting that the resistance arises from mutations in specific active transport mechanisms. Overall, these data demonstrate that fosfomycin enhances the uptake of tobramycin, resulting in increased inhibition of protein synthesis and ultimately bacterial killing.

Vanadium pentoxide (V(2)O(5)) induced mucin production by airway epithelium

Exposure to environmental pollutants has been linked to various airway diseases and disease exacerbations. Almost all chronic airway diseases such as chronic obstructive pulmonary disease and asthma are caused by complicated interactions between gene and environment. One of the major hallmarks of those diseases is airway mucus overproduction (MO). Excessive mucus causes airway obstruction and significantly increases morbidity and mortality. Metals are major components of environmental particulate matters (PM). Among them, vanadium has been suggested to play an important role in PM-induced mucin production. Vanadium pentoxide (V(2)O(5)) is the most common commercial source of vanadium, and it has been associated with occupational chronic bronchitis and asthma, both of which are MO diseases. However, the underlying mechanism is not entirely clear. In this study, we used both in vitro and in vivo models to demonstrate the robust inductions of mucin production by V(2)O(5). Furthermore, the follow-up mechanistic study revealed a novel v-raf-1 murine leukemia viral oncogene homolog 1-IKK-NF-κB pathway that mediated V(2)O(5)-induced mucin production. Most interestingly, the reactive oxygen species and the classical mucin-inducing epidermal growth factor receptor (EGFR)-MAPK pathway appeared not to be involved in this process. Thus the V(2)O(5)-induced mucin production may represent a novel EGFR-MAPK-independent and environmental toxicant-associated MO model. Complete elucidation of the signaling pathway in this model will not only facilitate the development of the treatment for V(2)O(5)-associated occupational diseases but also advance our understanding on the EGFR-independent mucin production in other chronic airway diseases.

MARCKS-related peptide modulates in vivo the secretion of airway Muc5ac

In a mouse model of neutrophil elastase-induced bronchitis that exhibits goblet cell metaplasia and inflammation, we investigated the effects of intratracheal instillation of the MANS peptide, a peptide identical to the NH(2) terminus of the myristoylated alanine-rich C kinase substrate (MARCKS) on mucin protein airway secretion, inflammation, and airway reactivity. To induce mucus cell metaplasia in the airways, male BALB/c mice were treated repetitively with the serine protease, neutrophil elastase, on days 1, 4, and 7. On day 11, when goblet cell metaplasia was fully developed and profiles of proinflammatory cytokines were maximal, the animals were exposed to aerosolized methacholine after intratracheal instillation of MANS or a missense control peptide (RNS). MANS, but not RNS, attenuated the methacholine-stimulated secretion of the major respiratory mucin protein, Muc5ac (50% reduction). Concurrently, elastase-induced proinflammatory cytokines typically recovered in bronchoalveolar lavage (BAL), including KC, IL-1beta, IL-6, MCP-1, and TNFalpha, were reduced by the MANS peptide (mean levels decreased 50-60%). Secondary to the effects of MANS on mucin secretion and inflammation, mechanical lung function by forced oscillation technique was characterized with respect to airway reactivity in response to cumulative aerosol stimulation with serotonin. The MANS peptide was also found to effectively attenuate airway hyperresponsiveness to serotonin in this airway hypersecretory model. Collectively, these findings support the concept that even in airway epithelia remodeled with goblet cell metaplasia and in a state of mucin hypersecretion, exogenous attenuation of function of MARCKS protein via the MANS peptide decreases airway mucin secretion, inflammation, and hyperreactivity.

A Novel, Orally Active CXCR1/2 Receptor Antagonist, Sch527123, Inhibits Neutrophil Recruitment, Mucus Production, and Goblet Cell Hyperplasia in Animal Models of Pulmonary Inflammation

Sch527123 [2-hydroxy-N,N-dimethyl-3-[[2-[[1(R)-(5-methyl-2-furanyl)propyl]amino]-3,4-dioxo-1-cyclobuten-1-yl]amino]ben-zamide] is a potent, selective antagonist of the human CXCR1 and CXCR2 receptors (Gonsiorek et al., 2007). Here we describe its pharmacologic properties at rodent CXCR2 and at the CXCR1 and CXCR2 receptors in the cynomolgus monkey, as well as its in vivo activity in models demonstrating prominent pulmonary neutrophilia, goblet cell hyperplasia, and mucus production. Sch527123 bound with high affinity to the CXCR2 receptors of mouse (K(d) = 0.20 nM), rat (K(d) = 0.20 nM), and cynomolgus monkey (K(d) = 0.08 nM) and was a potent antagonist of CXCR2-mediated chemotaxis (IC(50) approximately 3-6 nM). In contrast, Sch527123 bound to cynomolgus CXCR1 with lesser affinity (K(d) = 41 nM) and weakly inhibited cynomolgus CXCR1-mediated chemotaxis (IC(50) approximately 1000 nM). Oral treatment with Sch527123 blocked pulmonary neutrophilia (ED(50) = 1.2 mg/kg) and goblet cell hyperplasia (32-38% inhibition at 1-3 mg/kg) in mice following the intranasal lipopolysaccharide (LPS) administration. In rats, Sch527123 suppressed the pulmonary neutrophilia (ED(50) = 1.8 mg/kg) and increase in bronchoalveolar lavage (BAL) mucin content (ED(50) =<0.1 mg/kg) induced by intratracheal (i.t.) LPS. Sch527123 also suppressed the pulmonary neutrophilia (ED(50) = 1.3 mg/kg), goblet cell hyperplasia (ED(50) = 0.7 mg/kg), and increase in BAL mucin content (ED(50) = <1 mg/kg) in rats after i.t. administration of vanadium pentoxide. In cynomolgus monkeys, Sch527123 reduced the pulmonary neutrophilia induced by repeat bronchoscopy and lavage (ED(50) = 0.3 mg/kg). Therefore, Sch527123 may offer benefit for the treatment of inflammatory lung disorders in which pulmonary neutrophilia and mucus hypersecretion are important components of the underlying disease pathology.

Temporal profile of forced expiratory lung function in allergen-challenged Brown–Norway rats

The Brown-Norway rat is often used to study the allergic pulmonary response. However, relatively little is known about the delayed phase reactions after allergen challenge in this species. To evaluate the temporal changes in lung function and elucidate the mechanisms involved in the delayed phase response, Brown-Norway rats were sensitized and challenged to aerosolized ovalbumin and lung functions were measured by forced expiratory maneuvers and forced oscillation for up to 10 days after a single antigen challenge. Statistically significant (P < 0.05) reductions in inspiratory capacity, forced vital capacity, functional residual capacity, peak expiratory flow and maximum mid-expiratory flow and increases in respiratory system resistance and elastance were seen by 1 to 3 days after ovalbumin challenge that returned to baseline by 10 days. The reductions in lung function after ovalbumin challenge were blocked by the corticosteroid, betamethasone (1 mg/kg, p.o.). Histological evaluation of lung tissue of sensitized rats demonstrated evidence of interstitial pulmonary edema, an increase in tissue eosinophils and an increase in Periodic Acid Schiff-positive cells in the airway epithelium. Bronchoalveolar lavage fluid samples showed large numbers of eosinophils and increased mucin content up to 6 days after antigen challenge. There was also an increase in wet-to-dry lung weight ratio in the lungs of sensitized rats after antigen. These results demonstrate that prolonged reductions in lung function occur after a single antigen challenge in Brown-Norway rats that is probably due to inflammatory processes producing interstitial pulmonary edema, mucus secretion and cellular influx into the lungs.